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Single crystal diamond membranes and photonic resonators containing germanium vacancy color centers
摘要： Single crystal diamond membranes that host optically active emitters are highly attractive components for integrated quantum nanophotonics. In this work we demonstrate bottom-up synthesis of single crystal diamond membranes containing the germanium vacancy (GeV) color centers. We employ a lift-off technique to generate the membranes and perform chemical vapour deposition in a presence of a germanium source to realize the in-situ doping. Finally, we show that these membranes are suitable for engineering of photonic resonators such as microdisk cavities with quality factors of ~ 1500. The robust and scalable approach to engineer single crystal diamond membranes containing emerging color centers is a promising pathway for realization of diamond integrated quantum nanophotonic circuits on a chip.
关键词： germanium vacancy,Diamond,microring,nanophotonics,membranes,cavity
更新于2025-09-10 09:29:36
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Low-frequency noise in irradiated graphene FETs
摘要： We present a quantitative analysis of the low-frequency noise in irradiated monolayer graphene. In this study, we repeatedly irradiate a back-gated graphene transistor with argon ions at 90 eV and measure its low-frequency noise and channel conductivity after each irradiation. Our results indicate that the noise amplitude decreases monotonically with the increasing density of vacancy defects. The combination of our low-frequency noise measurements and carrier transport studies reveals that the mobility fluctuation model can explain this observation and that the density of vacancy defects, the density of charged impurities, and the mean free path of charge carriers determine the noise amplitude.
关键词： mobility fluctuation model,low-frequency noise,charged impurities,irradiated graphene,vacancy defects,mean free path
更新于2025-09-10 09:29:36
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Deterministic Arrays of Epitaxially Grown Diamond Nanopyramid <i>s</i> with Embedded Silicon-Vacancy Centers
摘要： The negatively charged silicon-vacancy center (SiV) in diamond is a potential high-quality source of single-indistinguishable photons for quantum information processing and quantum electrodynamics applications. However, when embedded in bulk diamond, this emitter suffers from both, relatively low extraction efficiency attributed to total internal reflection as well as nondeterministic location. On the other hand, its implementation in nanodiamonds is impeded by optical dephasing owing to their degraded surface quality. Here a robust and deterministic template-assisted bottom-up process for the creation of high-quality diamond nanopyramids incorporating SiVs is reported. This method employs a predefinition of high-precision nanopillars by e-beam lithography and dry etching, and subsequent epitaxial overgrowth during which Si atoms are introduced into diamond. The overgrown layer, including the nanopyramid arrays, is epitaxial as confirmed by comprehensive analyses. This diamond nanopyramid, hosting the SiVs, can pave the way toward efficient localized single-photon source arrays and potentially outshine nanodiamonds and nanosized structures prepared by a top-down method. The lateral confinement of the SiVs inside the deterministic nanosized pyramids enables their positioning at the center of cavities and optical structures for enhanced quantum efficiency and light–matter manipulation, and their employment as a system to explore collective coherent interactions between ensembles and confined light.
关键词： nanopyramids,field enhancement,spatial addressing,silicon-vacancy centers,diamond
更新于2025-09-10 09:29:36
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Carbon Vacancies in a Melon Polymeric Matrix Promote Photocatalytic Carbon Dioxide Conversion
摘要： Photosynthetic conversion CO2 into fuel and chemicals is a promising but challenging technology. The bottleneck of this reaction lies in the activation of CO2, owing to the chemical inertness of linear CO2. Herein, we present a defect engineering methodology to construct CO2 activation sites by implanting carbon vacancies (CVs) on the melon polymer (MP) matrix. Positron annihilation spectroscopy confirms the location and density of the CVs in the MP skeleton. transform spectroscopy and density functional theory (DFT) study reveals that the CVs can function as active sites for CO2 activation, while stabilizing COOH* intermediates, thereby boosting the reaction kinetics. As a result, the modified MP-TAP-CVs display a 45-fold improvement in CO2-to-CO activity over the pristine MP. The apparent quantum efficiency of the MP-TAP-CVs achieves 4.8 % at 420 nm, which exceeds most of the heterogeneous reduction of CO2 under visible light. This study will shed new light on the design of high-efficiency polymer semiconductors for CO2 conversion.
关键词： Carbon nitride,Photocatalysis,CO2 reduction,Carbon vacancy
更新于2025-09-10 09:29:36
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Controllable Synthesis of Inverse Opal TiO2-x Photonic Crystals and Their Photoelectric Properties
摘要： In this study, inverse opal TiO2-x photonic crystal (IO-TiO2-x) has been successfully synthesized by a two-step calcination. The whole synthesis is safe and feasible. Additionly, the reduction degree and the structure of IO-TiO2-x can be precisely controlled. A series of IO-TiO2-x samples with different reduction degree were prepared and characterized. The TEM images show that the obtained samples possess a 3D-ordered macroporous inverse opal structure. The reduced Ti atoms/oxygen vacancies were confirmed by Raman and XPS spectra results. All the IO-TiO2-x samples showed better photoelectric properties than those of common TiO2 which indicates great potential to be applied to photoelectric fields. The improvement of photoelectric properties is attributed to the efficient electron-hole separation efficiency induced by moderately reduced Ti atoms/oxygen vacancies. Meanwhile, the 3D-ordered macroporous inverse opal structure and the bandgap are regulated to “capture” more solar energy. This new approach is proves to be a meaningful method to synthesize high-performance TiO2 material.
关键词： reduction,oxygen vacancy,TiO2-x,inverse opal
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Electron Paramagnetic Resonance Study on a 28Si Single Crystal for the Future Realization of the Kilogram
摘要： In the future realization of the kilogram using the x-ray crystal density method, isotopically enriched silicon crystals grown by the floating zone method are employed. In this paper, we present the electron paramagnetic resonance study on 28Si single crystal AVO28. We revealed that the concentrations of various kinds of vacancy defects in the crystal are less than 1 × 1012 cm–3. Consequently, the necessary mass deficit correction due to these vacancy defects is estimated to be less than 0.4 μg for 1 kg AVO28 spheres.
关键词： electron paramagnetic resonance,silicon crystal,measurement uncertainty,kilogram,vacancy defects
更新于2025-09-10 09:29:36
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Increased nitrogen-vacancy centre creation yield in diamond through electron beam irradiation at high temperature
摘要： The nitrogen-vacancy (NV) centre is a fluorescent defect in diamond that is of critical importance for applications from ensemble sensing to biolabelling. Hence, understanding and optimising the creation of NV centres in diamond is vital for technological progress in these areas. We demonstrate that simultaneous electron irradiation and annealing of a high-pressure high-temperature diamond sample increases the NV centre creation efficiency from substitutional nitrogen defects by up to 117% with respect to a sample where the processes are carried out consecutively, but using the same process parameters. This increase in fluorescence is supported by visible and infrared absorption spectroscopy experiments. Our results pave the way for a more efficient creation of NV centres in diamond as well as higher overall NV densities in the future.
关键词： diamond,nitrogen-vacancy centre,high temperature,fluorescence,absorption spectroscopy,electron beam irradiation
更新于2025-09-10 09:29:36
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Effects of Ag Doping and Point Defect on the Magnetism of ZnO
摘要： The magnetism sources and magnetic mechanism of Ag doping and point defect, which coexist in the presence of ZnO, are frequently controversial. To solve these problems, the effects of Ag doping and Zn or O vacancy on the magnetism of ZnO were investigated using geometry optimization and energy calculation according to the first-principles generalized gradient approximation + U (GGA+U) method of density functional theory. Results revealed that the system which Ag doping and Zn vacancy coexists in ZnO could achieve room-temperature ferromagnetism. This system had an extremely high spin polarization, which was advantageous for the spin electron injection sources applied in dilute magnetic semiconductors. Result also revealed that the magnetism of Zn14AgO16 was caused by the electron hybrid coupling effects among the O-2p, Ag-4d, Ag-5s, and Zn-4s orbits. And these effects were produced by the hole carriers after complexes were formed by the Ag doping and Zn vacancy. With regard to the most stable structure of the ground state, all doping systems which Ag replacing Zn and O vacancy coexisted in ZnO and those which Ag replacing Zn, interstitial Ag, and O vacancy coexisted in ZnO were all non-magnetic. Thus, these doping systems were unsuitable for dilute magnetic semiconductors. By contrast, the doping systems of interstitial Ag and Zn vacancy were magnetic, although the magnetism was relatively weak, thus rendering such systems inapplicable as well.
关键词： Point defect,Ag doping,ZnO,Magnetism,First-principles,Vacancy
更新于2025-09-10 09:29:36
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Influence of defects in porous ZnO nanoplates on CO2 photoreduction
摘要： Photocatalytic conversion of CO2 into hydrocarbons by utilization of the solar energy is considered a promising approach to mitigate energy crisis and the environmental issues. Since the defects in a catalyst play an important role in CO2 reduction, herein, the porous ZnO nanoplates with vacancy defects are synthesized by annealing ZnS(en)0.5 precursor in air at different temperature. The defect amount in ZnO changes with the annealing temperature, resulting in different photocatalytic activity for CO2 reduction. The related mechanism has been studied both experimentally and theoretically. Raman spectra and chemical composition of the obtained catalysts are used to determine the defects. Transient techniques are used to investigate the separation of photogenerated charge carriers. CO2 adsorption capacity for different catalysts is also measured. First-principles calculation is used to study the adsorption and activation of CO2 on the ZnO surface. We envision that this work may afford an efficient approach to develop the semiconductor photocatalysts with superior activity via defects engineering.
关键词： Photoreduction,CO2,ZnO,Vacancy
更新于2025-09-10 09:29:36
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Effective protect of oxygen vacancies in carbon layer coated black TiO2-x/CNNS hetero-junction photocatalyst
摘要： Carbon layer coated black TiO2-x/g-C3N4 nanosheets (C@TiO2-x/CNNS) heterojunction photocatalysts were successfully prepared via a polydopamine dopamine carbonization route for the first time. It was found that the hydrogen evolution rate of C@TiO2-x/CNNS was 417.2 μmol h-1 g-1 under visible light irradiation, which was much higher than that of other prepared photocatalysts in solar water splitting process at the same conditions, and obvious decrease in catalytic activity can be observed after three recycles. The formation of carbon layer on the surface of TiO2-x can effectively protect Ti3+ and oxygen vacancies (Ovs) from oxidation by air and dissolved O2, afterwards much more Ti3+/Ovs are exsited, which can serve as charge carrier traps to inhibit the recombination of light-excited electrons-holes. Therefore, C@TiO2-x/CNNS showed a highly conductivity, rapidly effective electron-hole separation and lower transmission resistance comprehensive consideration of the advantages of carbon layer and hetero-junction, which are of great benefit to the improvement of photocatalytic performance. Hence, a new catalytic tactic namely layer-protection effect was founded and this strategy for boosting hydrogen evolution and protection Ti3+/Ovs may give us some hints on the design of photocatalytic systems.
关键词： black TiO2,visible light H2 evolution,g-C3N4 nanosheet,carbon layer protect oxygen vacancy
更新于2025-09-10 09:29:36